Development of Unipolar Ion Generator--Separation of Ions in Axial Direction of Flow

Although ions in the atmosphere play important roles in nucleation and gas-phase chemical reactions, their dynamic behavior is not well understood, To study ion behavior, reliable techniques for ion generation and measurement are needed. In this work, we describe a stable unipolar ion generator using an 241Am source, and an improved version of the ion counter and Faraday cage electrometer by reducing deposition of ions in these instruments. The new ion generator produced unipolar ions at concentrations as high as 1 X 10 \3 m - 3. The improved ion counter measured the ion concentration as low as 2.5 X 108 m - 3 at a flow rate of 1.5 L/ min,